Energy storage device

ABSTRACT

An energy storage device comprises a capacitor having a dielectric between opposite electrodes and a nonconductive coating between at least one electrode and the dielectric. The nonconductive coating allows for much higher voltages to be employed than in traditional EDLCs, which significantly increases energy stored in the capacitor. Viscosity of the dielectric material may be increased or decreased in a controlled manner, such as in response to an applied external stimulus, to control discharge and storage for extended periods of time.

FIELD OF THE INVENTION

This invention relates generally to an energy storage device, and, moreparticularly, to an electro-active electrical component used to storeenergy electrostatically in an electric field.

BACKGROUND

There has been a recent trend in the use of electrochemical capacitorsfor enhanced storage of electrical energy. These capacitors derive theirenhanced characteristics from two primary mechanisms: double layercapacitance and pseudocapacitance. Double layer-type capacitors use anelectrical double layer (explained below) to achieve a very small chargeseparation (d), which increases electric field (E) for a given voltage,increases capacitance (C) and consequently increases the energy stored(U) for the given voltage versus a conventional planar surfacecapacitor, as apparent in Eqs. 1 through 3 below.

$\begin{matrix}{E = \frac{V}{d}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

-   -   where E=electric field, V=potential difference or voltage, and        d=separation of charged plates.

$\begin{matrix}{C = \frac{k\; ɛ_{0}A}{d}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

-   -   where k=relative permittivity or dielectric, C=capacitance,        ∈₀=permittivity of free space, and A=cross-sectional surface        area.

$\begin{matrix}{U = {\frac{1}{2}{CV}^{2}}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$

-   -   where U=energy stored, C=capacitance and V=voltage.

Practically, the smaller thickness (d) allows for much more surface areaof the plates to be packaged (usually rolled or stacked) in a givenvolume. As evident from Eq. 2, this area increase also significantlyincreases capacitance. Devices of the above described nature arecommonly referred to as electric double layer capacitors (EDLCs).

In pseudocapacitors, which are a hybrid between double-layer capacitorsand batteries, both the bulk and the surface of the material play keyroles. They thus can store much more energy than conventional planarsurface capacitors, but face many of the same reliability and scientificchallenges as advanced batteries, including high cost due to expensiveraw materials and complex processing. Pseudocapacitance imitates batterytechnology by storing energy in chemical reactions (oxidation andreduction) which take place at or very near the surface of the relevantelectrodes. The surface nature of the reactions is the distinguishingcharacteristic from chemical battery technology.

Either or both of these effects (i.e., double layer andpseudocapacitance) may be used in so called “supercapacitors.”Advantageously, the invention herein makes use of and extends doublelayer theories in a novel manner, without any formal “chemicalreactions” present.

Also previously explored is the notion of enhancing a double layercapacitor by the application of an electrically conducting polymer e.g.Hu, U.S. Pat. No. 8,164,881. While the invention described hereincertainly makes use of a polymer coating, the polymer is sometimeselectrically resistive and sometimes insulating but is not electricallyconducting by design. This significantly differs in structure, natureand consequently in function from previous applications.

Current EDLCs can handle only low voltages before breakdown. In order toattain the higher voltages necessary for many practical applications(such as electric vehicles), low voltage EDLCs are connected in seriesmuch in the same way batteries are series-connected for high voltageuse. An energy storage device constructed according to principles of theinvention can handle higher voltages and be connected in series.

The invention is directed towards overcoming one or more of thefundamental problems with existing designs and solving one or more ofthe needs as set forth above.

SUMMARY OF THE INVENTION

To solve one or more of the problems set forth above, in an exemplaryimplementation of the invention, an energy storage device comprises acapacitor having a first conductive electrode having a first outer sideand an opposite first inner side; a thin non-porous first nonconductivecoating on the first inner side of the first conductive electrode; adielectric material on the first nonconductive coating, the firstnonconductive coating being disposed between the first conductiveelectrode and the dielectric material; and a second conductive electrodeadjacent to the dielectric material, the dielectric material beingdisposed between the second conductive electrode and the firstnonconductive coating. Optionally, a second nonconductive coating may beprovided on the second conductive electrode, disposed between the secondconductive electrode and the dielectric material. The nonconductivecoatings are thin, having a thickness that is less than 10% of theoverall thickness of the energy storage device. Illustratively, andwithout limitation, the nonconductive coatings may be comprised of acondensed and polymerized xylylene monomer, a parylene polymer,Puralene™ polymer, a metal oxide, or some other insulator that can bedeposited or otherwise formed in a thin film on the electrode(s).

The nonconductive coatings constitute insulating layers that allow formuch higher voltages to be employed than in traditional EDLCs. Thisextends the layers from just a few (two or three which alternate incharge) to many (possibly orders of magnitude more in number) which canreach far into the dielectric medium. The increase in working voltage,significantly increases the electric field present in the capacitor andenergy stored in the capacitor.

In one embodiment, the dielectric material is a variable viscositydielectric material. In other words, the viscosity may be increased ordecreased in a controlled manner, such as in response to an appliedexternal stimulus. By way of example, the external stimulus may be aforce, a pressure, a shear stress, a normal stress, heat, a heat sink, acoolant, a magnetic field, or an electric field. The external stimulusmay comprise a mechanism from the group consisting of a controllableheat source, a heat sink, a coolant, a controllable cooling source, acontrollable magnetic field generator, a controllable electric fieldgenerator, a controllable force generator, a controllable pressuregenerator, or a controllable shear stress generator. Viscosity of thedielectric can be made to gradually increase from electrode layer toelectrode layer sequentially, or vice versa. With a viscosity increase,the discharge of the Helmholtz and Diffuse Helmholtz layers as thermalenergy can be slowed and essentially halted with completesolidification. Electrical energy can thereby be stored for extendedperiods of time until ready for release. When ready for release, theviscosity may be reduced in a controlled manner such as by removing aviscosity-increasing stimulus or by applying a viscosity-decreasingstimulus. The reduction of viscosity facilitates discharge.

The dielectric material may be comprised of a dielectric substance suchas a conductive polymer, a nonconductive polymer, an inorganic metaloxide, a metal oxide mixture, a biopolymers or some other dielectricsubstance with a changeable viscosity. Electro-rheological dielectricsubstances, magneto-rheological dielectric substances and Binghamplastic dielectric substances may be used within the spirit and scope ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other aspects, objects, features and advantages of theinvention will become better understood with reference to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a schematic diagram that conceptually illustrates theHelmholtz model of an electric double layer; and

FIG. 2 is a schematic diagram that conceptually illustrates theGouy-Chapman model of an electric double layer; and

FIG. 3 is a schematic diagram that conceptually illustrates the Sternmodel of an electric double layer; and

FIG. 4 is a schematic diagram that conceptually illustrates the Grahamemodel of an electric double layer; and

FIG. 5 is a schematic diagram that conceptually illustrates the model ofan electric double layer by Bockris, Devanathan and Muller; and

FIG. 6 conceptually illustrates an exemplary energy storage deviceaccording to principles of the invention;

FIG. 7 conceptually illustrates an exemplary energy storage device withapplied forces according to principles of the invention;

FIG. 8 conceptually illustrates a flow diagram for producing a polymerfor use with an exemplary energy storage device according to principlesof the invention;

FIG. 9 is an exemplary flow chart illustrating a method for making ahigh permittivity dielectric material for use in an energy storagedevice according to principles of the invention; and

FIG. 10 conceptually illustrates a multi-state electrical circuitdiagram in accordance with one or more embodiments of the presentdisclosure for the recovery of leakage current from an energy storagecapacitor;

FIG. 11 conceptually illustrates a multi-state electrical circuitdiagram in accordance with one or more embodiments of the presentdisclosure for the recovery of leakage current from an energy storagecapacitor;

FIG. 12 conceptually illustrates a multi-state electrical circuitdiagram in accordance with one or more embodiments of the presentdisclosure for the recovery of leakage current from an energy storagecapacitor;

FIG. 13 conceptually illustrates a multi-state electrical circuitdiagram in accordance with one or more embodiments of the presentdisclosure for the recovery of leakage current from an energy storagecapacitor;

FIG. 14 illustrates voltages over time for an exemplary energy storagedevice according to principles of the invention.

Those skilled in the art will appreciate that the figures are notintended to be drawn to any particular scale; nor are the figuresintended to illustrate every embodiment of the invention. The inventionis not limited to the exemplary embodiments depicted in the figures orthe specific components, sequence of steps, configurations, shapes,relative sizes, ornamental aspects or proportions as shown in thefigures.

DETAILED DESCRIPTION

In an exemplary embodiment of an energy storage device according toprinciples of the invention, an insulating layer directly allows formuch higher voltages to be employed than in traditional EDLCs. This inturn increases the number of layers from just a few (two or three whichalternate in charge) to many (possibly orders of magnitude more innumber) which can reach far into the dielectric medium. A treatment asseries capacitors (a common way to analyze multilayer capacitance)demonstrates that, for a set amount of charge, adding more layers willactually decrease capacitance and increase voltage. This increase inworking voltage (both directly and indirectly from the use of aninsulating layer) along with the small degree of charge separationpreviously observed in EDLCs, significantly increases the electric fieldpresent in the capacitor as can be seen from Eq. 1 (above). Worthfurther notice is the resulting dramatic increase in energy stored inthe capacitor from the voltage increase as seen in Eq. 3 (above). Whileparameters can be manipulated to retain high capacitance (such as usingstacks, rolls, and other “tricks”), the increase in voltage clearlyoutweighs the proportional decrease of capacitance in the contributionsto the amount of stored energy of the overall device.

As background, the first mathematical description of an electricaldouble layer is thought to have been written by Hermann Helmholtz. Hedepicted two parallel layers of dissimilar charge along a surface. Thismodel gave a constant capacitance based on the separation of the layersand the dielectric properties of the medium. Helmholtz proposed that theinterface between a metallic electrode and an electrolyte solutionbehaves like a capacitor in that it is capable of storing an electriccharge. The Helmholtz model is conceptually illustrated in FIG. 1.Helmholtz's proposed model is that the electrode possesses a chargedensity arising from an excess negative or deficiency of positivecharges at the electrode surface. In the model, the charge on theelectrode is exactly balanced in solution by an equal but oppositelycharged amount of ions. This charge originates from the arrangement ofelectrolyte ions at the interface and/or the reorientation of dipoles insolvent molecules. A potential difference occurs across the interface,forming an electric field gradient across a charge separation layer.Ions are electrostatically repelled or attracted towards the electrodesurface and an excess of either anions or cations is created.

Upon observation that the capacitance was not truly constant withincreasing potential (voltage), the Gouy-Chapman model was introduced.Gouy employed statistical mechanics to develop his theory and suggestedthat the thermal motion of the medium prevents the formation of anorganized layer. The Gouy-Chapman model (FIG. 2) employs diffuse layersof charges which are quite unstationary. Gouy and Chapman proposed thediffuse double layer model that predicted a dependence of the measuredcapacitance on both potential and electrolyte concentration. They showedthat the excess charge density in solution is not exclusively situatedat the outer Helmholtz plane, and thus the double layer may be ofvariable thickness. In their view, a Helmholtz-type rigid double layerwould not form because the attractive and repulsive electrostatic forcesbetween the field and the charge on the ions are counteracted by randomthermal motion in the dielectric solution which tends to disperse theexcess ions from the surface of the electrode. In the Gouy Chapmanmodel, the ions are considered as point charges contained within asingle diffuse layer. This model, like the Helmholtz model, fails underparticular conditions.

Failures of the Helmholtz and Gouy-Chapman models prompted thecontributions of Stern and then Grahame. Their work combined the twopreviously mentioned theories into one in which an inner “Stern layer”or “Helmholtz layer” is organized on a charged surface with a diffuselayer forming around it. In the Stern model, as conceptually illustratedin FIG. 3, the two previous models were combined, with some of the ionsadhering to the electrode as suggested by Helmholtz and some forming aGouy-Chapman type diffuse layer. Grahame proposed that, although theclosest approach to the electrode is occupied by solvent molecules, itmay also be possible for some ionic or uncharged species to penetrateinto this region. This model for the electrode/electrolyte interface(FIG. 4) employs three regions. First, the inner Helmholtz plane orlayer extends from the electrode to a plane passing through the centersof specifically adsorbed ions. Second, the outer Helmholtz plane orlayer passes through the centers of hydrated ions at their distance ofclosest approach to the electrode. Third, the diffuse layer lies beyondthe other layers. Potential ψ changes linearly with distance up to theouter Helmholtz plane and then exponentially through the diffuse doublelayer region.

Still more work has been done to improve upon the theory by Bockris,Devanathan, and Muller who take into account solvent interactions in thedielectric. This model (illustrated in FIG. 5) is yet imperfect andoperates on assumptions such as the approximation of ions as pointcharges, the constancy of dielectric permittivity, the constancy ofviscosity, and the assumption that the significant interactions are allCoulombic in nature. Bockris, Devanathan and Muller suggested thatreorientation of solvent molecules would occur depending on the excesscharges at the electrode and the presence or absence of specificallyadsorbed ions at the surface. The proposed variation of theelectrostatic potential with distance is qualitatively similar to thatof the Grahame model. Water molecules cover most of the electrode in anoriented layer. At certain sites, the water molecules are replaced by aspecifically adsorbed ion (e.g., an anion) that has shed its hydrationshell. The plane going through the center of these ions is the innerHelmholtz plane, defining the inner Helmholtz layer. Ions that carry aprimary hydration shell are found next to and are situated outside ofthe first layer of water molecules adsorbed onto the electrode surface.The plane going through the centers of these ions constitutes the outerHelmholtz plane, defining the outer Helmholtz layer. None of thesemodels teach or suggest an energy storage device with an insulatinglayer or a variable viscosity dielectric according to principles of theinvention.

In the prior art it has been assumed that the energy stored in variouslynamed layers adjacent to the electrodes is non-recoverable. In otherwords, when an electric potential is applied to a flat electrode incontact with a solution that has ions capable of movement through thesolution, a movement of ions to that surface takes place. Once nearenough to the electrode, the ions are assumed to be immobilized at thesurface due to the strong electrostatic forces that bind them in place.The energy of collisions with solvent molecules is not sufficient todisplace these ions. If the electric potential is removed from thesurface, these ions are free to move about in a diffusive manner. It isinteresting to note that if the electric potential is removed from theelectrode surface, the resulting collapse of the electrical bilayerclosest to the electrode allows the release of energy of the immobilizedions such that the energy is not fully released as heat, but instead theelectrode can absorb the energy produced by the collapsing electricalfield and produce an electric potential and current in that conductor.This effect is the basis for the energy storage in an electrical doublelayer capacitor (EDLC).

The energy that is stored in the diffuse outer layers of an EDLC isoften not fully recovered. The electrical double layers that are formedclose to the electrode surface are termed Helmholtz layers, while thosethat are further away are termed the Gouy-Chapman layers. Onedistinction between these layers is that the ionic layers that are notcapable of being thermally diffused from the electrical surface aretermed “Helmholtz” layers. These layers are essentially immobilized atthe working temperature by the application of an electric potential tothe surface. Another distinction is that the diffuse Helmholtz layers(Gouy-Chapman, but often referred to as Diffuse Helmholtz layers),referred to as DH layers herein, are layers wherein random thermalmovements are able to diffuse the ionic arrangements induced by theelectric field. Since this is not a sharp boundary, an arbitrary timeunit associated with a 50% loss of potential energy over a period of 1second could be used to define the boundary layer conditions between thetwo major macroscopic layers.

Both the Helmholtz and DH layers (which form at constant ambienttemperature) are entropically reduced as compared to the bulk. Theseentropically modified materials display different physicalcharacteristics that have been noted (e.g. permittivity). Application ofthe modified characteristics has been shown in U.S. Pat. No. 8,633,289,to be issued Jan. 21, 2014, which describes improved synthesis of thestable intermediate dimer of xylylene ([2,2′]paracyclophane) andderivatives related to that compound and general structure, a method forthe formation of cyclophanes and related compounds with varioussubstituents, and a method to apply the xylylene (or substitutedxylylene) monomers to make coatings and other polymer products derivedfrom the reactive intermediate. Likewise, U.S. patent application Ser.No. 13/853,712, published as U.S. Publication No. 2013-0224397 on Aug.29, 2013, describes, inter alia, a method for making high permittivitydielectric material for capacitors using organic polymers to produce lowconductivity dielectric coatings.

The rationale for enhanced permittivity in entropically reducedmaterials is understood by the concept of the charges being “organized”into discrete rows and columns. Since each charge layer is energeticallyoptimized to be in the lowest energy configuration possible based uponsurrounding ionic charges, the imposition of an external electric fieldfrom the electrode leads to disruption of the lowest energy stateattainable from its current position. Thus, when the electric field isapplied, the dipole or ion is moved from its rest position, which inturn leads to a rearrangement of the charge distribution in thematerial. This leads to other rearrangements of all other dipolescontinuing throughout the dielectric. Thus, energy that is not convertedinto heat is absorbed by the dielectric. When the energy is released, areverse of this process can take place provided the energy stored is notreleased through other mechanisms such as increased thermal motions.

In the case of entropically “normal” materials, the rearrangement of thedipoles and ions in an electric field is not as certain to cause arearrangement of all the other ions and dipoles in the materials. Inother words, there is a probability that the rearrangement of the dipoleor the ion can take place with little or no net interaction with theother dipoles and ions in the material. In these cases, the materialwill display less energy storage capability than in its entropicallyreduced form.

If the viscosity of the material is such that movement of the moleculesis able to take place, the energy stored from the formation of theelectric field by a given dipole or ion is able to dissipate throughrelaxation mechanisms in which the energy is converted into rotation,vibration, translation, and other movements that manifest themselvesexternally as heat. With a low viscosity material, the energy that hasbeen stored in the Diffuse Helmholtz layers (DH layers) is thus lost dueto random motions of the ions and dipoles.

With intermediate to high viscosity materials, the time frame forformation of the Helmholtz layers (H layers) and the DH layers issubstantially increased. The thermal motions of molecules (excluding fornow vibrations of the lattice as a macroscopic phenomenon), however, areeffectively reduced to near negligibility. In these materials, it ispossible to store the energy of an electric field in the H and DH layersrelatively quickly compared to the time required for the energy to bedissipated thermally. Thermal dissipation is essentially a first orderdecaying exponential in time similar to radioactive decay or diffusion;if during the charging cycle the energy is absorbed over a time periodof, for example, 1 second, a high viscosity material may require manyseconds or even minutes to reach even 90% energy dissipation as heat.

The thermal decay process is substantially slower than the electricaldouble layer energy storage process. Thus, it is possible to utilize theenergy stored by the formation of both the H and DH layers if the energyis quickly accessed. In this situation the release of most of the energyin the formed dipole and ionic layers is through the electric field andis subsequently coupled with electric potential and current. Since thedischarge of the H and DH layers may require the movement of moleculesand atoms, the discharge process can be relatively slow compared tocharging but still remain fast relative to the relaxation mechanismsthat produce heat.

As conceptually illustrated in FIG. 6, in an exemplary embodiment, anenergy storage device according to principles of the invention includesa conductive electrode 105 having a smooth or rough surface, which, byexample, may be comprised of a smooth metal, a conductive polymer or arough carbon electrode of high surface area. A resistive or insulativecoating 110 is applied to one surface of the electrode 105. By way ofexample, the coating 110 may comprise a metal oxide, Puralene™, plasmaor film coating. A method of producing a Puralene™ coating is describebelow. Puralene™ is applicant's trademark for the coating substancedescribed below. A dielectric material 115, i.e., a high permittivitymaterial or a dipole containing low viscosity material, is applied tothe outer surface of the coating 110. By way of example, the dielectricmaterial 115 may comprise a conductive or nonconductive polymer, aninorganic metal oxide, mixed metal oxides, mixed polymer and organicmaterials and biopolymers. Nonlimiting examples of other suitabledielectric compositions are described below. In a preferred embodiment,the low viscosity of the dielectric may be increased in a controlledmanner by application or removal of energy in the form of heat, a force,electric field, magnetic field or other means of changing viscosity ofthe applied dielectric composition. The dielectric 115 may have itsviscosity reduced to aid in the more rapid release of the energy fromthe bound dipole and ionic layers. An opposite conductive electrode 125(which may be comprised of a conductor with insulative or resistivecoating or without such a coating) is applied to the dielectric 115,i.e., the high permittivity material or dipole containing low viscositymaterial. The opposite electrode 125 may be the same material as thefirst electrode 105. An insulative or resistive coating 120 between theopposite conductive electrode 125 and the dielectric 115 is optional.This coating 120 may be the same as the coating 110 between the firstelectrode 105 and the dielectric 115.

The electrodes may be attached to a voltage source, via conductive leads130, 135 (e.g., conductive wire leads, traces or other pathways), andallowed to charge. The viscosity of the dielectric 115 thus charged isoptionally increased to allow for a longer period of electric chargestorage due to the resulting decrease in random thermal motions or otherviscosity-dependent processes. The dielectric is discharged by currentflow out of the electrodes 105, 125 by an electrical load.

In a capacitor formed in this manner, equivalent charges of oppositesign will flow to each of the electrodes 105, 125. If the dielectric 115(i.e., high permittivity material or a dipole containing low viscositymaterial applied to the surface of the resistive or insulative coating)of low viscosity is used, the charge flow will be very substantial foran extended period of time. Very viscous materials require much longercharging times at lower rate of charge flow. Once charge has been addedfrom a voltage source, removal of the voltage source will then lead to aslow discharge of the voltage retained at the electrodes. The leakagecurrent resistively discharges the energy stored in the formation of theH and DH layers.

The thicker the insulative coating 110, 120 the higher the externalapplied voltage needs to be in order to store a given amount of energyat constant thickness. Additionally, thicker insulative coatings 110,120 such as PET (polyethylene terphthalate) produce an almost order ofmagnitude reduction in the energy storage capabilities. A Puralene™coating is preferred due to its characteristics of reduced pinholes,i.e., being substantially nonporous, and its ability to be coated intovery thin layers. This enables the overall thickness of a capacitor tobe in the range of 100 microns and reasonable voltages are thuspossible. For example if the thickness were 1000 microns and theinsulative coatings 110, 120 were 1% of that thickness (5 microns each),then to attain a 10V/micron e-field, 10,000V would have to be applied onthe cap externally. This is too high of a voltage to be usedeconomically and safely. Thus, the thinner the nonconductive coating110, 120, the lower the voltage can be while retaining the storagecapabilities of the device. Using Puralene™, which is inexpensive andexhibits very desirable qualities such as reduced pinholes, flatness,etc., and the high molecular weight ionic polymers salts described belowfor the dielectric 115, energy densities that are at least 10 times thatof typical EDLCs are achievable. FIG. 14, which is discussed below,illustrates the differences in performance of an energy storage deviceaccording to principles of the invention, in contrast to that of aconventional EDLC and batteries.

Viscosity modifiers, such as solvents, branched polymers, low molecularweight oligomers, and dendritic polymers may be added to the dielectricmaterial 115 to reduce viscosity. Ethanol and unreacted startingmaterials may serve such purposes.

Due to the viscosity dependence of the charging and dischargingcharacteristics of the system, it is advantageous to include in theembodiment of this technology a method for dynamically varying theviscosity of the dielectric. There are a multitude of known methods forefficiently creating a controllable change in the viscosity of a fluid,many of which could easily be integrated into the system implementationby one well-versed in the art of materials sciences.

One non-limiting example of a method for controlling the viscosity ofthe dielectric is by controlling the temperature. If instead ofmaintaining the device described above at a constant temperature, duringor after charging the device is cooled from an electrode 105 or 125inward, then the viscosity of the dielectric can be made to graduallyincrease from electrode layer 105 to electrode layer 125 sequentially,or vice versa. Assuming a viscosity increase with lower temperature(although the opposite effect can sometimes be obtained) the dischargeof the H and DH layers as thermal energy can be slowed and essentiallyhalted with complete solidification. The electrical energy can therebybe stored for extended periods of time until ready for release.

Release of the electrical energy with minimal losses to heating issimilar to the manner that it was charged. The cooled device can bewarmed as necessary with ambient heat or generated heat to releaseelectrical energy through the electrodes as the viscosity of theinternal dielectric is reduced. This slow warming has the added benefitof preventing rapid discharge of the energy contained in the H and DHlayers. Coordination of the warming of the electrodes and dielectric canbe made to accommodate the energy demands of the electrical load. Caremust be taken in the system design in order to prevent a runawaycondition in which internal or external heating of the dielectric causesthe temperature to rise rapidly and in turn decrease viscosity at anincreasing, uncontrolled rate.

Another well-known method for viscosity control is via exploitation ofnon-Newtonian fluid effects. A multitude of materials exhibit, tovarying degrees, a nonlinear or offset relationship between viscosityand applied stress, shear rate, time, or other factors. Applied forcesand pressure are conceptually illustrated in FIG. 7. Common materialshave been noted which exhibit either an increase or decrease in apparentviscosity when subjected to mechanical stress. These materials are oftenclassed as shear thickening (dilitant) or thinning (pseudoplastic),depending on the sign of the viscosity change. Many materials in thisclass exhibit viscoelastic effects, in that they have a tendency toreturn to their original shape once stress is removed. Additionally,other materials exhibit time dependence on viscosity with stress(thixotropic and rheopectic fluids, again depending on sign), and stillothers exhibit an offset relationship between viscosity and stress. Thelatter, known as a Bingham plastic, is of particular interest in thisapplication due to its specific characteristics.

A Bingham plastic is a viscoelastic material that behaves as a rigidbody at low stresses but flows as a viscous fluid at high stress. Morespecifically, a Bingham plastic is known to act as a solid when appliedstress is below a given limit, and therefore has a measurable yieldstress or other factors. By manipulation of this feature, a dielectricwhich acts as a Bingham plastic could be held in a solid state underlow-stress conditions, preserving H and DH layer formations for anextended period of time. When it becomes necessary to release the energystored within said layers, a varying amount of stress would be appliedto the dielectric, thereby controllably lowering it's viscosity.

The makeup of the dielectric could be chosen such that it exhibits adesirable set of non-Newtonian fluid characteristics. The embodiment ofthe device could then be engineered such that stress could be appliedthrough mechanical or other means to appropriately control the viscosityof the dielectric. For a non-limiting example, the capacitor stack couldbe placed between two plates. The bottom plate would be fixed in place,while the top plate is attached to a mechanical, electromagnetic,hydraulic, or pneumatic actuator. When it becomes desirable to applystress to the material, the actuator could apply force in a linear orrotational direction so as to apply the optimal amount, rate, andcombination of shear and normal stresses deemed most suitable to thefluid application. Alternative methods include using a hydraulic orpneumatic bladder to apply stress on the capacitor stack between twofixed plates, as well as surrounding the device with a shape memoryalloy, electroactive ceramic, dielectric elastomer, or other activeelement.

A combination of these effects may also be used to effect a change inthe dielectric's viscosity. By combining a non-Newtonian shearthickening dielectric fluid with low stiffness and compliant electrodes,the capacitor forms what is known as an electroactive polymer orspecifically a dielectric elastomer actuator. Once a charge is appliedto this capacitor, the electrostatic force between the electrodes causesa force directed normal to both plates. This force effectively“squishes” the dielectric together, applying a normal stress to thedielectric. If this dielectric were also a non-Newtonian shearthickening fluid, the viscosity would increase as the applied shearstress increases.

The viscosity of the dielectric material could also be dynamicallycontrolled by the modification of its physical characteristics toenhance the dielectric's viscoelectric properties. In a viscoelectric orelectro-rheological fluid, the makeup and structure of the dielectricfluid causes enhanced reactivity to external electric fields. An appliedelectric field can cause extreme, rapid, and reversible changes inviscosity. Electrorheological fluids can behave as a Bingham plastic,described previously, such that the yield stress is proportional to theapplied electric field. The design of the electrode has been shown toincrease electro-rheological effects. Much in the same way, thedielectric may be designed to exhibit magneto-rheological effects, whichwill respond to a magnetic field rather than an electric one. Themagneto-rheological effects may be even more applicable through lack ofinterference with the energy storage mechanism of the device.

In the case of both the dielectric elastomer actuator and viscoelectricembodiment, care must be taken to avoid a runaway condition. Because theviscosity of the fluid is determined by the field magnitude applied toit, specific conditions such as short circuit are especially dangerous.If a short circuit condition is allowed to exist, the charge on theelectrodes would be rapidly removed and therefore the viscosity of thedielectric fluid would decrease rapidly. This decrease in viscositywould greatly increase the mobility of the H and DH layers, causingrapid discharge of stored energy into a potentially dangerous (i.e.short circuiting) load.

In one exemplary capacitor according to principles of the invention one105 or both electrodes 105, 125 (each of which may be a smooth copperelectrode for example) may be coated using a Puralene™ coating process.Referring now to FIG. 8, a high level flowchart that illustrates anexemplary method of producing an augmented permittivity material, e.g.,Puralene™, for use as a coating in a capacitor according to principlesof the invention is shown. Sections, referred to as chambers, maycomprise tanks having an inlet and an outlet or tubular structures withan inlet and an outlet. Chamber 210 is a heated tube or otherevaporation device intended to volatilize starting material feed 200.Starting material feed 200 is evaporated and mixed with inert gas 205 inchamber 210. Inert gas 205 may be any of a group, or a mixture of, inertor essentially inert gases, such as, but not limited to, argon ornitrogen. Substitution of nitrogen for argon and/or other essentiallyinert gases is possible. Pumps and valves may be used to propel andcontrol the flow of fluids from one station to another.

By way of example and not limitation, chamber 210 may comprise anelectrically heated Inconel (nickel alloy 600) pyrolysis reaction tube.The tube is heated to a temperature of about 450° C. to 630° C. atatmospheric pressure. A flowing stream of argon gas alone, or with areactive compound such as nitrous oxide, is supplied to the pyrolysisreaction tube. The starter material feed 200 may be xylene vapor(Aldrich #134449-4L). If the carrier gas 205 includes a reactive speciesor compound (e.g., N₂O), the ratio of gases is adjusted to provideapproximately molar stoichiometric ratios of 1:1 of the reactive speciesor compounds (xylene to nitrous oxide).

The heated starter material 200 in the volatile mixture with inert gasreacts with monatomic oxygen in reaction chamber 215. Being veryreactive and transient, monatomic oxygen must be available to react withthe volatile mixture in the reaction chamber 215. As discussed above,the source of monatomic oxygen may be a gaseous compound supplied withthe carrier gas 205, or a gaseous compound supplied separately 240, oranother source, such as a plasma generator 235.

Monatomic oxygen plasma may be created by exposing oxygen (O₂) gas to anionizing energy source, such as an RF discharge, which ionizes the gas.Alternatively, a compound such as Nitrous Oxide (N₂O) may supplymonatomic oxygen for the reaction through thermal, catalyzed, and/orother decomposition. Thus, a monatomic oxygen plasma generator 235, or amonatomic oxygen chemical compound (e.g., N₂O) feed 240, or anothersuitable source of monatomic oxygen is provided.

A plasma gas can be used with the aforementioned starting materials toform the intermediate oxidized products that may subsequently react toform reaction products that are oxidized forms of the starting materialswhich may be monomers, dimers, trimers, oligomers, or polymers. Theplasma generator 235 includes a gas feed 230 that supplies gas to aplasma reaction chamber 220. A plasma driver 225 provides energy toionize the gas.

The ratio of gases is adjusted to provide approximately molarstoichiometric ratios of 1:1 (xylene to nitrous oxide or xylene tomonatomic oxygen). Illustratively, increased amounts of nitrous oxideresult in partial and/or complete oxidation of xylene with reducedformation of the desired cyclophane or its polymer. Close control of thestoichiometric ratios of the reactants is desired in this reaction.

The reaction products are supplied to a reaction chamber 235, which isheated to approximately 450° C. to 800° C. to facilitate vaporization ofthe reaction products. The vaporized reaction products 245 are expelledonto a lower temperature collection surface 250, where the reactionproducts condense and form a solid. At higher temperatures (650° C. to800° C.) the output of the reaction chamber 235 is sufficiently hotenough to maintain the monomer p-xylylene in monomeric form.

Condensation of the gas into a cooled glass vessel resulted in thedeposition of a colorless to cream colored solid. This solid ispartially soluble in 95% ethanol. The solid was compared to a sample of[2,2′]paracyclophane (Aldrich #P225-5G-A) by Gas Chromatography analysis(SRI#310, 15 m megabore column, FID detector) and was shown to giveidentical retention times.

Rapidly cooling of the monomer onto a surface 250 (which, such surface,may comprise a surface of an electrode 105, 125) results in a liquidcondensation of the monomer and rapid polymerization of the monomer intoa polymer. Comparison of the film thus produced appears to be identicalto parylene film formed by the conventional vacuum pyrolysis of dimersproduced by the Gorham process. Without augmentation of the Puralene™polymer, permittivity of both solidified products is about 3, electricbreakdown strengths are about identical at 100 V/micron, and solubilityin both hot and cold solvents are below detectable levels.

In this reaction it is believed that the reactive p-xylylene reactiveintermediate is formed and subsequently may be dimerized in the reactiontube 235 or during condensation 245 onto the substrate 250. Thisreaction used to synthesize the dimer, in comparison with the known“Gorham process”, results in a vast improvement in the overall synthesisyield of the dimer and also results in a vast improvement in the purityof the dimer directly from the reaction. It is understood that variationin the stoichiometric amounts of the reactants may be adjusted toprovide for greater or lesser yield with associated purities varying toprovide a more economical process or better overall productionefficiency without substantially deviating from the scope of thisinvention. Subsequent purifications of the materials from this reactioncan be performed on this material in a manner that is much easier toaccomplish than with previously taught processes. The reaction is shownbelow.

As the reaction temperature at station 235 is increased to >650° C., thedeposition of the xylylene monomer can proceed directly onto a solidsubstrate target without necessity for isolating the intermediate dimer.Deposition of the exit gas at above 650° C. reaction temperature upon acool glass plate resulted in formation of an ethanol insoluble substancethat displays characteristics of a parylene polymer. However, observedsolubility characteristics clearly show that the material is insolublein all common solvents (i.e. hexane, xylene, ethyl acetate, ethanol,water).

It is believed that the reaction mechanism proceeds through a routeinvolving the prior decomposition of nitrous oxide. Nitrous oxide is anenergetically unstable molecule that can be thermally decomposed atelevated temperatures. Products of the reaction are diatomic nitrogenand monoatomic oxygen. The monoatomic oxygen is able to react withitself to form diatomic oxygen, but this reaction is relatively slow.Estimates vary determining the temperature that pure thermaldecomposition occurs, but estimates of 1100° C. are often cited.Catalysis of this reaction as shown below in equation 1 is known tooccur with a variety of metal oxides and mixed metal oxides. Sometemperatures used for nitrous oxide decomposition with certain catalystsare as low as 350° C.

The reactive species for the process is very likely the monoatomicoxygen produced from the decomposition of the nitrous oxide. In thissense, the nitrous oxide can be viewed as a convenient carrier for thedelivery of the reactive intermediate, monoatomic oxygen.

In a similar manner to the nitrous oxide reaction, pure diatomic oxygencan be utilized as a reactant. However, to produce substantial yields ofthe desired products, activation of the oxygen is necessary. It isbelieved that activation of the oxygen is due to the excitation of theoxygen molecule to produce monoatomic oxygen as shown in Equation 3.

The reaction with monoatomic oxygen produced in this manner thusproceeds in a manner similar to that of the nitrous oxide decompositionroute.

Cooling of the elevated temperature gases 245 exiting from the reactiontube 235 is necessary. If the reaction gas is at too high of atemperature, the ability of the reactive intermediate to condense andadhere to a surface is greatly reduced. To this end, a device to mixcool nonreactive or inert gases into the hot reaction stream has beendevised. The reaction may proceed at increased or decreased pressure(above or below atmospheric pressure). Accordingly, an expansion valvemay be used at the exit of the reaction tube 235 to provideJoule-Thomson effect cooling of the hot gas when the gas is below itsinversion temperature.

The method may be extended to other substituents such as the ones shownbelow.

Substituents such as the ones noted above (chloro, dichloro, methoxy,and methyl) are not the only aromatic substituents that are capable ofbeing modified by this process into reactive intermediates and theirsubsequent polymers. Additionally, paracyclophanes and compounds derivedthereof are not exclusive to this process. Meta and ortho orientation ofthe substituents on the aromatic rings are also viable reaction startingmaterials. The reaction can be generalized to include all compounds thatare capable of reaction with monatomic oxygen produced from a plasma orfrom decomposed oxygen-containing substances or its intermediatereaction products and also contain hydrogen atoms stabilized by thepresence of an aromatic ring. Typically such hydrogen atoms are locatedin a position alpha to a phenyl ring (benzylic position). Michaelstructures removed from the alpha aromatic ring positions are known togive similar reactivity to the hydrogen alpha to the aromatic ringposition as is well known to those versed in organic synthesis. However,the reactivity of such hydrogen atoms is not limited to alpha and/orMichael positions from an aromatic ring or the aromatic ring such asbenzene. Other aromatic stabilizations are known for many differentrings, fused rings, and non-ring systems, as known to those versed inthe art of organic chemistry. Such starting materials may preferablyhave the presence of two hydrogen atoms that are capable of beingremoved to form partially oxidized starting materials. These preferredmaterials may optionally have the ability to dimerize, trimerize,oligiomerize, or polymerize. The nonlimiting example used herein isp-xylene.

One implementation of the invention augments permittivity of the polymerby exposing the condensing reaction products 245 to a magnetic orelectric field. To the output of the reactions described above, thegaseous stream of reaction product 245 is directed to a cool solidsurface 250. Illustratively, the surface target 250 may be immersed in amagnetic field 255 such as that provided by a Neodymium magnet (S84, K&JMagnetics). Other magnetic field sources may be utilized and areintended to come within the scope of the invention. Condensation of themonomer and subsequent polymerization can proceed rapidly while in themagnetic field 255. If the target and the magnet maintain the samerelative orientation during the polymerization process, then a baselineincrease in the electrical permittivity has been shown to occur. If theorientation of the magnetic field 255 relationship to the target isrotated during the polymerization or solid phase condensation process,then the resulting permittivity has been shown to decrease.

When the reaction is conducted as noted above, using the p-xylylenemonomer as the polymerization molecule, but without the presence of theapplied magnetic field the relative permittivity of the materialdeposited is approximately 3. When the material is run as described witha magnetic flux 255 density of approximately 200 to 2000 Gauss, therelative permittivity is approximately 7. Thus, the magnetic field hasbeen shown to substantially increase the permittivity of the product byover a factor of 2 times. In a similar manner other salts, dipoles, andsalts of organic acids can be entropically oriented duringsolidification or polymerizations to produce enhanced high permittivitymaterials. Improvements in permittivity from 10 to over 1000% may beattained.

In another implementation, the surface target 250 is immersed in anelectric field 255 such as that provided by a high voltage power supply(G40, Emco, 4000V). Condensation of the monomer and subsequentpolymerization can proceed rapidly while in the electric field. If thetarget and the electric field maintain the same relative orientationduring the polymerization process, then a baseline increase in theelectrical permittivity has been shown to occur. If the orientation ofthe electric field relationship to the target is rotated during thepolymerization or solid phase condensation process, then the resultingpermittivity has been shown to be lower.

Condensation of dielectric reaction products in the presence of anelectric and/or magnetic field, has been shown to augment thepermittivity of the condensed dielectric. This step may be applied tocompounds other than parylene polymers.

When the condensation step is conducted as noted above, using a mixtureof maleic acid salt with guanidine as a high dielectric material, butwithout the presence of the electric field the relative permittivity ofthe material deposited is approximately 500. When the material isprocessed as described with an electric field density of 10,000 to30,000 V/m, the relative permittivity is approximately 25000 to 40000.Thus, the electric field has been shown to substantially increase thepermittivity of the dielectric field by at least a factor of 25 in thatparticular case. In a similar manner other salts, dipoles, and salts oforganic acids can be entropically oriented during solidification orpolymerizations to produce enhanced high permittivity materials.Improvements in permittivity have been shown to range from 5 to over10000%.

The use of electrical and/or magnetic fields during the condensationprocess modifies the mechanical strength of the product. The materialmay not be anisotropic after condensation in strong fields. Thus, thismethod could be utilized as a way of controlling the mechanicalproperties of the reaction products made by this procedure.

The thickness of a Puralene™ coating 110, 120 may range from 5 to 30 nmto greater than 10 microns. The coated electrode 105, 125 is then usedas the basis for application of the dielectric material 115.

Dielectrics that may be used to form a capacitor according to principlesof the invention abound. However, to produce a substantially improvedenergy storage device, it requires more than simply making a dielectricand putting it between two electrodes. The method whereby the dielectricis selected, transformed, and applied is of critical importance and notobvious to those skilled in the art of capacitor manufacture.

In an exemplary implementation, a viscosity stratified dielectric for anenergy storage device according to principles of the invention may beformed from 15 grams of protein powder (such as Zein, Sigma-Aldrich#Z3625), to which 50 ml of absolute ethanol is added. The solution iswell stirred under inert atmosphere until complete dissolution isobtained. To this solution is added portion-wise 10 g of maleicanhydride (Sigma-Aldrich #M188) solid with vigorous stirring for a totalperiod of 30 min. The solution is heated to 60° C. during this period oftime. At the end of the period 0.5 g of dicumylperoxide (Sigma-Aldrich#329541) is added portion-wise over 5 min. The solution is allowed toboil and stir at above 60° C. for 1.5 h. The solution is cooled to roomtemperature. Then solid guanidine carbonate (Sigma-Aldrich# G1165-9) isadded portion-wise until the solution is neutral to basic. A resultinghoney colored liquid may be used in the dielectric. Alternatively, othermaterials such as copolymerized maleic acid/acrylic acid (Sigma-Aldrich#416053) may be neutralized with guanidine to produce similar results.Alternatives to guanidine may be used as well. For non-limiting example,Cesium carbonate and Rubidium carbonate may be used as substitutes.Other organic, polymer, and inorganic cationic species may besubstituted. Ultrahigh molecular weight acrylic acid/acrylamides arealso possible dielectrics when they are optionally neutralized to theirsalts forms.

FIG. 9 is an exemplary flow chart illustrating a method for making ahigh permittivity dielectric material, according to an embodiment of thepresent disclosure. The method begins by dissolving an organic polymerin a solvent to form a slurry solution (305). The polymer may beshellac, silicone oil, zein, and/or another organic polymer. In oneembodiment, the undissolved organic polymer is removed from the slurrysolution (310), for non-limiting example, using a filter or centrifuge.An inorganic salt may then be added to the slurry solution (315). Theinorganic salt may be a transition metal salt, such as a Gd, Sr, Sn, Fesalt, or a mixture thereof. In one embodiment, a breakdown voltageadjuvant may be added to the slurry solution (320). The breakdownvoltage adjuvant may include one or more of Y, Ni, Sm, Sc, Tb, Yb, La,Te, Ti, Zr, Ge, Mg, Pb, Hf, Cu, Ta, Nb, Bi, or a mixture thereof. Tofacilitate screening and drying, a dimethyl formamide and adimethylsulfoxide may be added to the slurry solution (325). The slurrysolution may then be heated to a temperature of about 150° C. to about300° C. to remove or evaporate the solvent (330). This method avoidshigh process temperatures and produces a high dielectric capacitor witha high breakdown voltage.

Other suitable dielectric materials include conductive polymers salts,such as salts of acrylic acid, acrylamides, methacrylates, polypyrole,etc.; inorganic metal oxide such as perovskites (i.e. barium titanate,strontium barium titanate, etc.); charged ionic liquids such as polymersalts and other electrically charged liquids or semi-solids that mayhave ability to migrate or move to some extent within a matrix; or amixture of these.

The applied dielectric material 115 has a second electrode 125 addedthat may be optionally coated with a nonconductive coating 120 such asPuralene™, using a coating process as described above. Connection of theelectrodes 105, 125 to a voltage source and a load via leads 130, 135 issimilar to that of a traditional electrostatic capacitor.

In another exemplary embodiment, a high surface area electrode 105, 125is used instead of a smooth electrode. This provides for a greatersurface capacitance and a faster discharge during the first phase ofdischarge. The high surface area electrode may comprise activated carbonor another conductive material which, when applied to the surface of theelectrode, exhibits high surface area. The adjacent electrode may becoated or uncoated.

In another embodiment, an energy storage device according to principlesof the invention may contain a dielectric material that has the propertyof changing viscosity. The methods for introduction of variableviscosity into the dielectric may comprise variable temperature,variable electric field, variable magnetic field, variable pressure,variable shear and/or normal stress. Variable pressure, shear and stressare each a type of application of force. The direction and distributionof the applied force determines whether it is a pressure, shear orstress.

An exemplary method of making a magnetorheological dielectric entailsdistributing electrically insulated (or non conducting) magneticparticles throughout the dielectric. Once the H and DH layers areformed, a magnetic field would be applied to increase the viscosity ofas well as to prevent particle migration through the dielectric and“lock in” the H and DH layers. Altering the magnetic field strengthwould allow controlled dissociation of the layers through chargemigration (current flow) within the dielectric itself. Also, the appliedmagnetic field could potentially introduce additional layering orentropic changes for energy storage.

An explanation of the mechanism whereby the energy is stored in thesedevices is proposed. Although useful for a working theoretical model, noexplanations offered herein in any way detracts from the inventivenessof the method or the processes described.

In general the largest mechanism for the initial charging current intothe energy storage devices noted above are through the capacitance-modeof the device. During the later energy storage phase of charging, thediffuse Helmholtz layer formations is the primary mode of energystorage. This DH mode is more easily accomplished when the dielectricmaterial is less viscous. This general rule is tempered by the fact thatcertain polymers can display more viscous characteristics while under anelectric field than not. However, the formation of the DH layers is morepronounced when the device is under a greater electric field. To preventthe dissipation of energy stored in the DH layers, it desirable to havethe viscosity increase after the electrical energy has been used to formthese layers. In this way dissipation of the energy is decreased andpotentially mitigated.

If there is dissipation of the energy thus stored through the electricalfield of the device, it may be advantageous to use an electronic circuitto recover at least a portion of the energy converted by “leakage” andsubsequently saved by storage into an external energy storage device orconsolidated and returned to the device itself.

Referring now to FIGS. 10-13, a multi-state electrical circuit diagramis illustrated in various states in accordance with one or moreembodiments for making an electronic device for the recovery of leakagecurrent from an energy storage capacitor. FIGS. 10-13 illustrates fourstates a novel circuit that has been developed to regenerate and recyclethe leakage current from a capacitor or capacitor array, C1.

In FIGS. 10-13, the following components are described. C1 is acapacitor or capacitor array that is capable of storing a certain amountof charge. It displays a leakage of current when subjected to a givenvoltage (V+). C2 is a capacitor (e.g., much smaller than C1) of goodstorage characteristics that displays a much lower leakage current (orcould be the same leakage current, but of much smaller area ofcapacitance). D1 is a diode that has the characteristic of being able to“block” the voltage from C1 from returning to Vss. When the voltageoutput from transformer T1's secondary coil exceeds the voltage presenton C1 and the forward voltage drop of D1, then current will conduct tothe C1 capacitor(s). S1 is a three position single pole switch. Line CLis a control line that controls S1. S1 is switch that is able toelectrically connect the high voltage side of C1 to the chargingvoltage, V+. In one position it is connected to V+ and in the otherposition it is an open connection (NC) or connected to the load (LOAD).S2 and S3 are electrically controlled switches that have the ability toswitch between two different outputs. These switches do not necessarilyneed to be high voltage switches able to withstand V+. T1 is a “flyback”type of transformer or an equivalent inductor that has the capability ofwithstanding a voltage on the secondary winding that is as great orgreater than V+. V+ is a charging voltage that is connected to the mainenergy storage capacitor(s) C1 during the charge cycle. Vss is the lowervoltage that is present on the opposite electrode of C1 from V+ thatproduces the potential difference between the two electrodes.

Using the multi-state electrical circuit of FIGS. 10-13, leakage currentmay be recovered and regenerated from a capacitor C1 according toprinciples of the invention. Referring to State A of the circuit diagramof FIG. 10, a current is shown flowing from the V+ source through S1 tothe positive plate of C1. In this situation S2 is connected to Vss suchthat the charge can be accumulated on C1 to the potential differencebetween the two. The status of S3 does not matter at this state and nocurrent is flowing in the lower part of the circuit.

In State B of the circuit diagram of FIG. 11, V+ has been disconnectedfrom the positive electrode of C1 and the other electrode of C1 isconnected to ground through S2. This illustrates a typical situationwhere the stored load of the C1 capacitor is being used through the S1switch to power an electrical load.

In States C and D of the circuit diagram of FIGS. 12 and 13, two statesare shown where the C1 storage capacitor is not being charged ordischarged. However, due to the leakage current from one electrode toanother, there is a current flowing through the non-ideal C1 componentto C2 through the S2 switch. This current will charge C2 to some voltageat a rate based upon the relative capacitances of C1 and C2 and the rateof leakage. The switch S2 is disconnected from ground and connected tothe input of C2. While in State C, the C2 capacitor is charged to somepredetermined voltage (V1). At that predetermined voltage, thecomparator then disconnects C2 from C1's open “Vss” electrode using S2,and S2 connects to “Vss”, and then subsequently connects the positiveelectrode of C2 to the input of T1 transformer using S3, as shown inState D of FIG. 13. This discharge current through T1 induces a voltageon the secondary of T1 that rises to a voltage value sufficient toreturn some of the charge to C1 through the diode D1. Once the dischargeof C2 is complete as determined by the comparator's determination ofvoltage on the positive electrode of C2, the comparator returns all theswitches to State C unless a demand is made to charge or discharge C1.

In the above-described operation, a relatively “leaky” capacitor canreturn some of the charge loss through the C1's leakage when C1 is notin use during either a charge or discharge period of time. Due to theefficiency of the circuit (which can be made to be >90% efficiency), theleakage from the C1 device is effectively reduced by a factor of up to 9times. For production of a large array of capacitors, this can be asignificant improvement in yield. Often there are unwanted impurities inthe material that increase the leakage current, and these are often notdetected until the entire assembly has been completed. In the case of alarge array capacitor, this amounts to a significant number of gooddevices being rejected due to a relatively small number of failures inthe array.

As the graph in FIG. 14 shows, a voltage charges one electrode of theenergy storage device, while a voltage is generated by the otherelectrode that is series connected to ground through a 10K resistor. Asthe device charges, there is a rapid charging of the electrode and lowimpedance due to the capacitance of the device. The capacitance modes ofcharging are much faster than the Helmholtz layer formations, butultimately much less charge is stored by these mechanisms for energystorage than by the DH layer formations.

Referring now to FIG. 14, energy and voltages over time for an exemplaryenergy storage device according to principles of the invention areconceptually illustrated. The energy storage device is a capacitor thatcharges through a resistor coupled to a 120 VDC source. Connection of aPicoScope™ Model 4262 to each electrode of the capacitor and utilizationof the scope's integrated math functions allow calculation and displayof the energy flowing into the circuit as shown by trace 405. Theapplied voltage to the first electrode is represented by trace415A-415B, and the displacement current is represented by the trace 410.The first charging voltage of approximately 120V supplies 8.16 J to thecapacitor. The second voltage of −120 VDC applied at approximately the 3minute mark shows an energy delivery of 8.08 J. In this particularcharge sequence the amount of charge and discharge are approximatelyequal. Integration of the displacement current across the capacitorreveals that the energy absorbed and the energy discharged areapproximately equal to within the error limits of the data acquisitiondevice and integration routine. Longer charge cycles could be used, butessentially all of the energy supplied in this period of time at thisvoltage has been absorbed by the capacitor in this time frame. Somedroop in the power supplies are present due to the low reactance of thecapacitor during initial switching. This voltage drop is accounted forin the calculations of the scope. In this example, the energy absorbedis 8.16 J. The volume of sample is 0.006333 ml. The energy density is1288 J/ml or 198 Wh/kg. Integration of the charge reveals thatessentially a >90% recovery of the charge can be obtained when thedischarge cycle is at least 10 times longer than the charge cycle.

In another example shown in Table 2 below, the charge stored is in therange of 0.41 Wh/kg at very low electric field magnitudes (0.34 V permicron).

TABLE 2 q C A d v E Vol. E/m³ ρ E/kg E-field 776,000 25,876 50 87 301.16E−2 4.35E−9 2.68E+6 1.8 0.413 0.34

q in (nA.s), C in μF, A in mm^(2,), d in μm, v in volts, E in J, Vol. inm³, ρ in g/cm³, E/kg in Wh/kg, E-field in V/μm.

Higher electric field magnitudes than noted in Table 2 above have beenused. Devices charged with larger magnitude electric fields store morecharge, and higher values for energy density per mass have beenobtained.

While an exemplary embodiment of the invention has been described, itshould be apparent that modifications and variations thereto arepossible, all of which fall within the true spirit and scope of theinvention. With respect to the above description then, it is to berealized that the optimum relationships for the components and steps ofthe invention, including variations in order, form, content, functionand manner of operation, are deemed readily apparent and obvious to oneskilled in the art, and all equivalent relationships to thoseillustrated in the drawings and described in the specification areintended to be encompassed by the present invention. The abovedescription and drawings are illustrative of modifications that can bemade without departing from the present invention, the scope of which isto be limited only by the following claims. Therefore, the foregoing isconsidered as illustrative only of the principles of the invention.Further, since numerous modifications and changes will readily occur tothose skilled in the art, it is not desired to limit the invention tothe exact construction and operation shown and described, andaccordingly, all suitable modifications and equivalents are intended tofall within the scope of the invention as claimed.

1. A capacitor comprising: a first conductive electrode having a firstouter side and an opposite first inner side; a first nonconductivecoating on said first inner side of said first conductive electrode; adielectric material on said first nonconductive coating, said firstnonconductive coating being disposed between said first conductiveelectrode and said dielectric material; a second conductive electrodeadjacent to said dielectric material, said dielectric material beingdisposed between said second conductive electrode and said firstnonconductive coating; and said capacitor having an overall thicknessfrom first conductive electrode to second conductive electrode, and saidfirst nonconductive coating having a thickness that is less than tenpercent of said overall thickness.
 2. A capacitor according to claim 1,further comprising: a second nonconductive coating on said secondconductive electrode and being disposed between said second conductiveelectrode and said dielectric material, said second nonconductivecoating having a thickness that is less than ten percent of said overallthickness.
 3. A capacitor according to claim 1, said dielectric materialbeing a variable viscosity dielectric material, said variable viscosityhaving a physical characteristic of exhibiting a change in viscosity inresponse to an external stimulus.
 4. A capacitor according to claim 3,said external stimulus comprising a stimulus from the group consistingof a force, a pressure, a shear stress, a normal stress, heat, amagnetic field, and/or an electric field.
 5. A capacitor according toclaim 3, said dielectric material having a physical characteristic ofincreasing in viscosity as the external stimulus is applied anddecreasing in viscosity as the external stimulus is removed.
 6. Acapacitor according to claim 3, said dielectric material having aphysical characteristic of decreasing in viscosity as the externalstimulus is applied and increasing in viscosity as the external stimulusis removed.
 7. A capacitor according to claim 3, said dielectricmaterial having a physical characteristic of releasing energy at a rate,said rate increasing as viscosity of the dielectric material decreases.8. A capacitor according to claim 3, said dielectric material having aphysical characteristic of releasing energy at a rate, said ratedecreasing as viscosity of the dielectric material increases.
 9. Acapacitor according to claim 3, said dielectric material having aphysical characteristic of receiving charge at a rate, said rateincreasing as viscosity of the dielectric material decreases.
 10. Acapacitor according to claim 3, said dielectric material having aphysical characteristic of receiving charge at a rate, said ratedecreasing as viscosity of the dielectric material increases.
 11. Acapacitor according to claim 1, said first nonconductive coatingcomprising a condensed and polymerized xylylene monomer.
 12. A capacitoraccording to claim 1, said first nonconductive coating comprising ap-xylylene polymer.
 13. A capacitor according to claim 1, said firstnonconductive coating comprising a metal oxide.
 14. A capacitoraccording to claim 1, said dielectric material comprising a viscosityreducing agent, and said dielectric material having a viscosity, saiddielectric material having a physical characteristic of exhibiting anincrease in viscosity from a first viscosity to a second viscosity inresponse to an external stimulus, and exhibiting a decrease in viscosityfrom the second viscosity to the first viscosity upon removal of theexternal stimulus.
 15. A capacitor according to claim 14, said externalstimulus selected from the group consisting of a controllable heatsource, a controllable cooling source, a controllable magnetic fieldgenerator, a controllable electric field generator, a controllable forcegenerator, a controllable pressure generator, and a controllable shearstress generator.
 16. A capacitor according to claim 1, said dielectricmaterial comprising a viscosity increasing agent, and said dielectricmaterial having a viscosity, said dielectric material having a physicalcharacteristic of exhibiting a decrease in viscosity from a firstviscosity to a second viscosity in response to an external stimulus, andexhibiting an increase in viscosity from the second viscosity to thefirst viscosity upon removal of the external stimulus.
 17. A capacitoraccording to claim 16, said external stimulus selected from the groupconsisting of a controllable heat source, a controllable cooling source,a controllable magnetic field generator, a controllable electric fieldgenerator, a controllable force generator, a controllable pressuregenerator, and a controllable shear stress generator.
 18. A capacitoraccording to claim 1, said dielectric material comprising a dielectricsubstance selected from the group consisting of a conductive polymer, anonconductive polymer, an inorganic metal oxide, a metal oxide mixture,a biopolymers, a viscoelastic.
 19. A capacitor according to claim 1,said dielectric material comprising an electro-rheological dielectricsubstance.
 20. A capacitor according to claim 1, said dielectricmaterial comprising a magneto-rheological dielectric substance. 21.(canceled)